A detailed review of physical regularities is presented in this paper to introduce the vapor- condensation model of deposition.

Peculiarities of the technique of the local laser-induced front transfer (LIFT) of thin films are investigated. Possible mechanisms of tearing-off and transference of the films from the donor substrate (target) to the acceptor one are considered. Thermal, gas-dynamical and hydrodynamical models are proposed for explanation and numerical estimation of a number of effects observed with local laser film deposition. Applications of the LIFT method are considered.

Investigations are carried out to characterize Cu deposition from a solid target using a XeCl, 28 ns pulse width, excimer laser at energies between 2 - 15 J/cm². Scanning electron microscope (SEM) studies of the target surface revealed sputtering effects, droplet formation and surface waves. Density per unit substrate area of droplet-like-Cu particles transferred from the target is a function of frequency, deposition time, state of the target surface and power density. Mass and charge collected at the substrate are obtained as a function of distance to the target. Mass deposition as a variation of laser beam to target angle, facetting angle at feature edges and grain size as a function of substrate bias were measured. Fill shape evolution of micron size holes are obtained. An energy threshold for Cu-ion generation is extrapolated from the measured ion current vs. energy in.

The regular structures formation on a silicon surface under the millisecond pulse of linear- polarized, circular-polarized and unpolarized Nd-laser light irradiation has been studied experimentally. The surface structures induced by the interference of incident wave and surface electromagnetic waves and also the double- and triple-period structures with periods d equals 2 - 3 microns were observed in the nonhomogeneous melting regime. The diffraction pattern separation at higher incident fluence and incident angles have been observed. The main peculiarities of the surface structures formation were explained by polaritonic mechanism.

The possibilities and advantages of UV-laser ablation technique for deposition of doped PbTe thin films are discussed. To understand the effects of experimental parameters on layer formation the stages of laser sputtering of the target and film growth were investigated. Method of laser ionization RETOF mass spectrometry was used to obtain the energy distribution and chemical nature of evaporated particles as a function of wavelength and laser radiation power. The influence of experimental parameters on the deposited film thickness, stoichiometry and crystalline perfection was checked. The dependence of doped PbTe films photoelectrical properties on the experimental parameters.

A continuous wave (CW) Nd:YAG laser operating at the fundamental mode of 1.064 micrometers was used to deposit CdS thin films with cubic phase on glass, quartz, NaCl (100), and carbon coated formvar substrates. At substrate temperatures near 200 degree(s)C, the films consisted of a combination of the zincblende (cubic) and wurtzite (hexagonal) phases of CdS. X-ray diffraction patterns of films deposited on each substrate indicate a predominantly cubic structure. Transmission electron microscope further confirmed the presence of the cubic phase. The films had a stoichiometric ratio of 1:1 for Cd:S. The surface of the films were optically smooth. Optical transmission measurements reveal a room temperature absorption edge of 515 nm for the films deposited on glass and quartz substrates. Raman spectra show longitudinal optical (LO) modes at 300 cm^-1 (1LO) and 605 cm^-1 (2LO), similar to that of the hexagonal film. The transition from predominantly cubic to hexagonal films was estimated to occur near 275 degree(s)C for glass substrates, and 350 degree(s)C for quartz substrates.

The mechanisms of UV induced decomposition of oxygen-deficient centers (ODC) in silica glass has been experimentally studied. It is shown that high intensity irradiation of silica glass results in the two-step decomposition of ODC and formation of paramagnetic E' centers. At the same time at low UV irradiation intensity (laser, mercury lamp) the single quantum reaction of ODC with gas-phase impurities in the net of silica is the dominant process of ODC photoreaction.

Hydrodynamic phenomena from KrF excimer laser ablation (10^-3-20 J/cm²) of polyimide, polyethyleneterephthalate, and aluminum are diagnosed by laser beam deflection, schlieren photography, shadowgraphy, laser-induced-fluorescence and dye-laser- resonance absorption photography (DLRAP). Experiments were performed in vacuum and gaseous environments (10^-5 to 760 Torr). In vacuum, the DLRAP diagnostic shows species-resolved plume expansion which is consistent with that of a reflected rarefaction wave. Increasing the background gas pressure reveals the formation of sound/shock compared to CN in the laser-ablated polyimide (Vespel) plume/shock in inert (e.g. argon) and reactive (e.g. air) gases. At low pressures (less than 10 Torr) Al and CN species are in close contact with the shock front. As the pressure increases, the species front tends to recede, until at high pressures (over 200 Torr) the species are restrained to only a few mm above the target surface. After sufficient expansion, Al and CN are no longer detectable; only the shadowgraph of the hot gas plume remains. Since CN is observable in both inert and reactive environments, it can be concluded that CN is not a reaction product between the background gas and the ablated species. By way of comparison to excimer laser ablation processing of materials, copper vapor laser machined polyimide and polymethylmethacrylate (transparent to green and yellow copper vapor laser light) are also investigated. The two polymers are observed to have markedly different machined surfaces. Hydrodynamic effects for the copper vapor laser machined materials are investigated using HeNe laser beam deflection.

In this work, we investigate the velocity distribution function of neutral yttrium atoms which appeared during the laser evaporation of different targets (pure metallic yttrium, yttrium oxide Y₂O₃, and high T_c ceramics YBa₂Cu₃O_7-x). We also investigate the influence of buffer gas and external electric field on the distribution function.

We studied the propagation of shock waves (SW) through the background air of various pressure and dissipation of gaseous disturbances near the irradiated target after its evaporation by a pulse laser. The SW and gas disturbances were observed with optical and piezoelectrical methods. The experimental data were compared with the point explosion theory.

We report ultrafast measurements of the dynamic thermal expansion of a surface and the temperature dependent surface thermal diffusivity using a two-color reflection transient grating technique. Studies were performed on p-type, n-type, and undoped GaAs(100) samples at several temperatures. Using a 75 fs ultraviolet probe with visible excitation beams, the electronic effects that dominate single color experiments become negligible; thus surface expansion due to heating and the subsequent contraction caused by cooling provide the dominant influence on the diffracted probe. The diffracted signal was composed of two components, thermal expansion of the surface and heat flow away from the surface, allowing the determination of the rate of expansion as well as the surface thermal diffusivity. At room temperature a signal rise due to thermal expansion was observed, corresponding to a maximum average displacement of approximately equals 1 angstroms at 32 ps. Large fringe spacings were used, thus the dominant contributions to the signal were expansion and diffusion perpendicular to the surface. Values for the surface thermal diffusivity of GaAs were measured and found to be in reasonable agreement with bulk values above 50 degree(s)K. Below 50 degree(s)K, the diffusivity at the surface was more than an order of magnitude slower than in the bulk due to increased phonon boundary scattering. Comparison of the results with a straightforward thermal model yields good agreement over a range of temperatures (12 - 300 degree(s)K). The applicability and advantages of the transient grating technique for studying photothermal and photoacoustic phenomena are discussed.

We present a model for the kinetics of laser-induced desorption of atoms from perfect nonmetallic surfaces, based on recent experiments in alkali halides and compound semiconductors. For the sake of specificity we consider situations in which the photon energy E_hv is less than the bandgap energy E_gap, so that the density of bulk electronic excitation created by the laser-surface interaction is small. We show desorption-yield calculations as a function of laser intensity for the case of solids with strong electron-lattice coupling (alkali halides) and weak-coupling solids (compound semiconductors). These distinctive features may allow extrapolation to the case of intermediate coupling which includes many technologically important oxides.

The absorption behavior of model polymeric systems is investigated in the low (< 50 mJ/cm²) and high (> 1 J/cm²) fluence regime at standard excimer laser ultraviolet wavelengths. The new technique of nanosecond time resolved thermometry is exploited to resolve the heating and cooling rate, as well as the total thermal load of a thin polymer film that is exposed to low fluence irradiation. The results suggest that a thermal model of heating and ablation is appropriate for these systems. This represents the first direct measurement of the time resolved heating of a strongly absorbing polymer system. In addition, a new nanosecond time resolved digital photographic technique has been used to image the shock wave and debris dynamics of a polymer undergoing high fluence ablation. These results suggest that, at high fluences, the total energy in the incident photon pulse can be entirely accounted for in the energy driving the shock wave.

The electrical conductivity of high temperature polymers (i.e. polyimide) has been changed permanently from 10^-17 (Omega) ^-1 cm^-1 to 10 (Omega) ^-1 cm^-1 by KrF (248 nm) excimer laser irradiation. The conduction mechanism is found to be phonon assisted variable range hopping between small (approximately 10 nm) carbon rich clusters that form a macroscopic percolation cluster. Using a holographic technique, periodic line structures with periods ranging from 166 nm to 950 nm have been produced in polyimide by direct ablation with a KrF excimer laser. Taking advantage of the large nonlinearity in the laser ablation process, linewidths ranging from 30 nm to several hundred nm could be obtained. This technique was combined with the ability to induce electrical conductivity in polyimide to produce an array of 500 nm wide electrically conducting wires. The conductivity of these wires was similar to that found in macroscopic regions of laser induced conductivity.

Ablation of polyimide with a XeCl excimer laser produces deposits of soot-like debris that can alter the surface properties of adjacent structures. In this case, debris accumulation degraded the quality of ultrasonic wire bonding to contaminated bond pads. The addition of flowing helium during the ablation process visibly reduced the debris accumulation and improved subsequent wire bonding. The quality of wire bonding was then used to measure the relative importance of ablation process parameters in the reduction of debris.

Nonlinear absorption dynamics are studied in C₆₀ solutions by measuring the nonlinear energy transmittance and transmitted temporal profiles of Q-switched doubled Nd:YAG pulses. The rate equations are solved for a five level system using a combination of analytical and numerical techniques via Mathcad with model parameters taken from the literature. Very good agreement is found with the nonlinear energy transmittance. The slight disagreement between the calculated and temporal profiles is discussed.

Experimental results show that 10.6 micrometers polarized laser beam does not normally reflect on germanium-chromium-aurum junction. Reflection angle is not equal to incident angle. There is divergence about 34 mrad. Injection of current into the junction gives magnitude modulation for laser beam reflected on the junction and the modulation relates to vibrational transition of CO₂ laser. The paper describes the results and possible theoretical explanations.

The response of YBa2Cu3O7-x surface to the short laser pulse action has been studied. The glow spectrum-time characteristics have been defined at different laser pulse energies. The mechanisms of phase change induced by laser light influence on the high temperature superconductor surface have been investigated. It has been established that the nanosecond pulse exposure caused the glow pulse response. Its spectrum and time characteristics measured during the pulse action time depend on the laser light power density and the environment temperature.

This review is devoted to critical analysis of the latest results in two new branches of study: photodesorption of resonant absorbing particles from a surface of transparent dielectrics and photodetachment of intrinsic atoms of a metal. We have investigated the former, taking as a sample under examination an Na atom absorbed on the surface of monocrystalline sapphire. As to photo processes that take place on the surface of a metal, their existence was assumed to be bound up with short wavelength radiation or electronic impact induced vacancies having long enough lifetimes in the inner shells of the near surface atom. As shown, this process is due to the existence of intrinsic structural defects of a metallic surface. The electronic states of such defects are more localized and possess long lifetimes of excited states and it is this fact which causes an efficiency of photodetachment event of an atom from a surface. The review shows the main properties of this phenomenon and discusses its concrete mechanisms.

The processes of the defects and the periodic structures formation on the silicon surface under the pulsed laser influence ((lambda) equals 1.06 micrometers , (tau) approximately equals 1.5 msec, EL approximately equals 3 J) have been studied. It has been shown that (1) at the energy densities FL thres (Fthres is the threshold energy density), formation of reversible defects took place, and at FL Fthres, irreversible defects appeared, (2) local melting of the surface started within the region where the defects formation occurred, (3) the periodic structures formation strongly depended on the mutual orientation vector of the crystallographic axes and the laser beam polarization.

The laser induced phase transitions in III-V compounds have been investigated by time resolved reflectivity. Raman scattering and Rutherford Back scattering techniques. It has been shown that an intensive evaporation of V-component from the laser melted crystal can initiate the solidification of the melt directly from the surface. This layer has a polycrystalline structure with (110) preferred orientation and is rather defective. The defect concentration is maximal at the border where the recrystallization front moving from the surface and that moving from the substrate are meeting.

The investigations of laser light interaction with a matter are of increased interest now because of the development and wide industrial applications of laser technique. Such processes as defects formation, diffusion, solid state chemical reactions and others may be initiated under the laser light influence. That, the growth of "huge" crystals on the surface of copper target irradiated by the carbon dioxide laser light has been detected by authors I1I. An anomalous mass transport of impurities induced by the laser light action has been observed in a number of materials. Thus, the penetration of carbon into titanium under the pulse laser light exposure (A = 1.06 411111, T =iO s, E=1O -120 J) and introduction of boron into steel patterns induced by a continuous carbon dioxide laser light have been investigated, and the penetration depths of impurities were found to exceed considerably those of radiation /2,3/. The intensive redistribution of the impurities is clearly determined by the phase transition proceeding. In work /4/, an unusual 5-6 orders increasing in the coefficient of interstitial impurities diffusion into V205 and an acceleration of the solid state reactions caused by resonance CO2 laser light have been demonstrated. Besides, the works on the diffusion stimulated by short wavelength radiation (2=44mm and .=66Onm, N - 1 /cm2) / 1 ,5/ are of profound interest now. In these experiments, the heat was supposed to be no more than 1K. Incidentally, the possible statement about the defects formation as a result of photo stimulation was considered to be improbable as requiring the high energy values (I < iO W/cm2) . Intense pulsed laser influence, which flux density exceeds the threshold value, causes the formation of the layers with a great number of nonstationary defects and is accompanied by high rate of the crystallization front movement (—lOm/s) /6,7/. Similar phenomena have been studied under the action of other types of high energy flux. For example, a perceptible acceleration of the phase formation induced by the electron beam with energy level of l2OkeV, crystallization and recrystallization /9/ , an anomalous transport of the interstitial impurities in both the metals and the transitional metals oxides / 10/ have been registered. It should be noted that all the phenomena considered are accompanied by abrupt grain growth and, consequently, by crystallization and recrystallization. The phenomena observed can not be explained with a heat model limit. The clear explanation for this phenomena is not accepted now, but one may suppose that the laser light induced weak nonstationarity in condensed matter changes substantially the processes behavior if the system state corresponds to the critical points of the equilibrium diagram. Such a situation may be realized, for example, during the chemical reactions and phase transformations. The transitional metals oxides (V205, Nb205, MoO3) were chosen as objects under examination, and the explanation for this choice lies in the possibility to form nonstationary defects states under the different types of laser influence.

The results are presented of local interferometry investigation of the microrelief evolution of silicon surface under the high power laser pulsed effect (Ppulse approximately equals 1 J, (lambda) equals 1.06 micrometers , (tau) pulse approximately equals 1.5 msec). It has been shown that the formation of the periodic microrelief is preceded by the excitation and concurrence of surface deformations of various types.

The regular structure formation on a silicon surface under the millisecond pulse of linear-polarized Nd-laser light irradiation has been studied experimentally. The surface structures induced by the interference of incident wave and surface electromagnetic waves and also the double-period structures with periods d — 2-3 microns were observed in the nonhomogeneous melting regime. The double-period structures formation was explained by polaritonic mechanism and was due to a nonlinear absorptance changes in semiconductor-metal phase transition.

Non-steady-state polarization response of photoexcited GaAs has been investigated with the specular micropolarimetry particularly in crystals with laser induced damages of near surface layer. Physical models of the polarization response in the excited GaAs due to electron-hole plasma photogeneration are discussed: the nonlocal electron-hole plasma model the optically induced piezogyrotropy the electrooptic effect in the Dember field. 1.